The present invention relates to a side impact airbag apparatus that is mounted on a vehicle to reduce impact applied to a side of the vehicle.
Side impact airbag apparatuses are known as devices that protect an occupant of a vehicle from impact due to a side collision with a side portion of the vehicle body such as a side door. Such an apparatus includes an inflator that discharges inflation gas in response to a vehicle side collision and an airbag that is inflated and deployed by the inflation gas supplied by the inflator. The inflator is incorporated in the airbag. The airbag and the inflator are stored in a portion of a vehicle seat that is close to an outer side of an occupant seated on the seat, for example, in an storage portion provided in a seat back (backrest portion).
In the above mentioned side airbag apparatus, when the body side portion receives an impact from the outside due to a side collision, the inflator discharges inflation gas into the airbag. The supplied inflation gas causes the airbag to shoot out from the seat back and pass through a narrow space between the occupant seated on the vehicle seat and the vehicle body side portion. The airbag is inflated and deployed into a size and shape capable of protecting the occupant. This type of airbag reduces the impact that is transmitted from the outside to the occupant through the body side portion.
The airbag and the inflator of the above described side impact airbag apparatus need to be stored in the storage portion in the seat back of a limited size. Therefore, when stored in the storage portion, the airbag is required to be in a compact form (form suitable for storage).
To meet such a need, an airbag in a deployed state is normally folded in the following manner before being stored in the storage portion. First, a portion of the deployed airbag that is forward of the inflator is folded from the front toward the rear, so that the airbag is folded into a transitional form elongated in the up-down direction. Next, a portion of the airbag in the transitional form that is below the inflator is folded forward, and the folded part is further folded from the front toward the rear. Through this folding process, the airbag becomes compact in the up-down direction as well as in the front-rear direction. For example, Japanese National Phase Laid-Open Patent Publication No. 2006-508846 discloses a folding process in which a portion of an airbag that is located below an inflator is folded from the front toward the rear as in the above described airbag.
When an inflator supplies inflation gas to an airbag that has been folded into the storage state described above and stored in an storage portion of a seat back, the airbag is first inflated and deployed forward while being unfolded, and then is inflated and deployed downward.
However, when the airbag is inflated and deployed downward after being inflated and deployed forward, the airbag cannot easily enter the narrow space between the body side portion and the lumbar region and a thigh of the occupant. The reasons for this are considered to be as follows. That is, when the airbag is about to enter the narrow space after inflated and deployed forward and then downward, the airbag may press the occupant downward against the seat cushion. If the occupant is pressed against the seat cushion, it is difficult to move the occupant inward with respect to the widthwise direction of the vehicle and to enlarge the space between the occupant and the body side portion. This hampers the airbag from entering the space between the occupant and the body side. Therefore, the airbag can hardly be deployed to reach a lower position between the occupant and the body side portion and reliably protect the occupant.
If an airbag is folded in such manner that the airbag is only folded from the front toward the rear so that the airbag has a thin shape extending in the up-down direction, the above described problem is largely avoided. This is because the airbag in the storage state is deployed to a low position from the beginning. However, in this case, the airbag has an elongated shape in the up-down direction. This complicates the process for storing the airbag in the storage portion of the seat back.